The mineralization of the small rock mass is a new academic concept proposed through the exploration and research of metallic sulfide deposit with the magmatic activity by Tang Zhongli, which is a popular characteristic in endogenic magmatic deposits. It is also a key to reveal the principle of metallogenesis for our ore-prospecting work. Here is a new definition and classification have been put forward based on years′ studies, including magmatic liquation and magmatic hydrothermal. The first type was composed of sulfide segregation and oxide segregation; second one was formed with water-hydrothermal metasomatism, filling metasomatism and contact metasomatism. There are four mechanism of mineralization of the small rock mass: deep segregation model, magma conduit model, pulse model and hydrothermal pulse model.